1. Field of the Invention
The present invention relates generally to conveying systems, and more particularly to reciprocating conveyors for semi-trailers, and still more particularly to a trailer having front and rear compartments, each with a moving slat reciprocating conveyor or live floor.
2. Discussion of Related Art Including Information Disclosed Under 37 CFR 1.97, 1.98
The installation and use of moving slat reciprocating conveyors, also known as live floors and/or walking floors, is well known. These conveyors are widely employed in material handling systems and in semi-trailers to address commercial challenges in storing and transporting bulk particulate materials—which, as used in the instant application, means such things as produce, particulate material of various kinds, including grain, hay, seed, livestock feed and fodder, sawdust, wood chips, mulch and compost, gravel, small rocks, fertilizer and other powdery substances, manure, refuse, and the like.
Live floors have found their broadest application in the loading and unloading of open end box-like enclosures (trailers, bins, silos, and storage containers, for example). Such structures pose a problem for front end loaders in moving bulk material into and out of the enclosure. Accordingly, one solution has been to provide a conveyor system within the enclosure that typically comprises a series of hydraulically powered floor slats in a side-by-side disposition to form a floor. Each of the slats is fabricated from aluminum, formed steel, or a lightweight alloy.
The general principle of operation for a partially enclosed live floor relies on friction, and can be stated simply: The weight and friction of a material on the surface area of two slats exceeds the weight and friction of a material on a third slat. Accordingly, a single slat can be moved underneath bulk material without appreciably moving the mass as a whole, as the other two slats hold the material in place. When all of the slats have been moved independently beneath the material away from the direction in which it is desired to move the material, they can then be moved in unison in the direction of unloading, thereby conveying the material. The timed sequence of the reciprocating movements ensures that nearby neighboring slats do not move together when moving in the direction from which the bulk material is to be moved, whereas they do move in unison to move material in the desired direction. Slat dimensions, including length, width and thickness, are generally governed by the intended use, and power is typically provided by a two-way, variable speed power unit, which powers hydraulic actuators to drive the floor slats.
A typical live floor unloading cycle proceeds as follows: In the first cycle stroke, all slats move in unison. This is a conveying movement. At the end of the first stroke, a first set of slats, comprising every third slat, moves under the load, but the load remains stationary. Next, a second set of every third slat moves under the load. Again, the load remains stationary. Finally, a third set of every third slat moves under the load, and again, the load remains stationary. The cycle is then repeated with all of the slats moving in unison to convey the load. Used in this manner and operated at demonstrated efficient speeds, unloading a typical 45-foot trailer with a live floor takes only a few minutes.
Exemplary systems enjoying broad market acceptance and commercial success include the Keith WALKING FLOOR®, made by Keith Mfg. Co of Madras, Oreg., and the HALLCO WALKING FLOOR® and Hallco LIVE FLOORS® made by Hallco Mfg. Company, Inc., of Tillamook, Oreg. These systems, when installed in a trailer, provide for the loading and unloading of a number of materials, including the bulk goods identified above. Such installations and use have been shown to reduce trailer floor cleaning time, destination dock turnaround time, payload cross contamination, cargo damage, and fuel consumption, while improving worker, material flow, productivity and throughput. And because a trailer tipper and an unloading hopper are not needed to offload cargo, a trailer equipped with a live floor allows the unloading of numerous kinds of material. Furthermore, trailers can be loaded from the top, rear end, and side. [WALKING FLOOR® is a registered trademark of R. Keith Foster, d.b.a. Keith Mfg. Co., of Madras Oreg. HALLCO WALKING FLOOR and LIVE FLOORS® are registered trademarks of Hallco Manufacturing Company, of Tillamook, Oreg.]
Exemplary prior art patents include U.S. Pat. No. 5,560,472, to Gist, which teaches a seal/bearing arrangement for a walking floor or conveyor system intended to prevent the inadvertent passage of particulate material through the floor members and into the area beneath the floor members.
Other instructive references include U.S. Pat. No. 5,325,957, to Wilken, which shows a live floor having continuous bearings that shield their contact surface on floor slats from liquid and other material or materials which are thrown toward the bottom of the floor slats and the continuous bearings.
U.S. Pat. No. 5,222,593, to Quaeck, discloses a reciprocating floor conveyor having a supporting frame, base members on the supporting frame, side-by-side slidable slats mounted slide on the base members, and hydraulic power system with flow regulators to provide a sequential retraction of the slat groups in a longitudinal reciprocative movement.
Also of interest are U.S. Pat. Nos. 4,896,761 and 4,858,748, to Foster, and U.S. Pat. No. 5,560,472, each of which, like the foregoing patents, discloses and teaches a solution to the problem of particulate materials dropping into the spaces between the side-by-side moving slats of a reciprocating live floor. This problem results in the loss of bulk material, the accumulation of particulate material in the spaces below the floor (and sometimes in machine parts), and eventually an undermining of floor system function.
The foregoing patents reflect the current state of the art of which the present inventor is aware. Reference to, and discussion of, these patents is intended to aid in discharging Applicant's acknowledged duty of candor in disclosing information that may be relevant to the examination of claims to the present invention. The general structural and operational elements of each of the foregoing references are considered well known and are incorporated in their entirety by reference herein.
However, it is respectfully submitted that none of the above-indicated patents disclose, teach, suggest, show, or otherwise render obvious, either singly or when considered in combination, the invention described and claimed herein. In particular, none of the foregoing systems provides a trailer with a live floor capable of hauling two different bulk materials. Accordingly, when there is a need to transport and deliver two different bulk commodities in loads comprising less than half a trailer of material, the materials are loaded into two different trailers that were either hauled separately or at one time in a double-trailer configuration. This prevents the two materials from mixing and contaminating one another. There thus remains the need to provide a trailer having a live floor which makes it possible to transport two different bulk commodities in a single haul.